The invention relates to a socket for mounting electrical parts such as IC packages in a freely detachable fashion to obtain an electrical connection with the electrical parts.
In the manufacture of semiconductor circuit chips (IC chips), it is generally the case that an IC package prepared by resin-sealing IC chips are subjected to reliability tests called "burn-in" as well as electric property tests prior to their shipment for the purpose of separating the good products from the defective products. In the electric property test, the input/output properties of the IC chips, pulse characteristics, and noise leeway, etc., are tested. In the "burn-in", those IC packages which have passed the electric property test are placed in an oven and made to function for a certain length of time at an elevated temperature as, for instance, 120 degrees centigrade and at a voltage level which is approximately 20 percent greater than the rated value. The IC packages that have not passed the "burn-in" are rejected as dissatisfactory products, with only those IC packages which have functioned normally being shipped out as satisfactory products.
In recent years, the IC packages of the vertical surface mount package (VPAK) type or of the surface mounting type, with leads being provided only on one side of the package, have become increasingly popular. The IC package of this type typically is mounted with the one side where the lead is provided on a printed substrate so that the package as a whole is installed in a vertical state. The use of these packages has the advantage of increasing the substrate mounting density.
A typical prior art structure of a socket for the conventional testing of an IC package of such a VPAK type is shown in FIGS. 16 and 17. FIG. 16 shows the state prior to the IC package being mounted on the socket and FIG. 17 shows the state in which the IC package has been mounted.
In these figures, the IC package 100 is of the VPAK type, with one row of leads 102 protruding on one side of the package. Since the IC package of this type tends to have the leads 102 easily bent by an external force, a carrier 104 is used when the package 100 is inserted in the socket. In carrier 104, IC package 100 is carried by a claw part 104b at the bottom of a movable piece 104a which is provided on the inner surfaces that face each other in the longitudinal direction of the carrier 104 and shown in FIG. 16. The bent tip part of the leads 102 is received by a protuberant part 104c which is provided on the carrier 104.
Socket 106 has a base 108 as the main socket body. At a prescribed location in base 108 at a location which corresponds to leads 102 of the IC package 100 that is to be mounted on the socket, a plurality of contacts 110 are provided in a row.
Each contact 110 is typically prepared by extruding a thin sheet of beryllium copper, or the like, and has a base edge 110a which is buried in the base 108, an arc spring part 110b which extends upward in a curved fashion from the top of this base edge 110a, a linear spring part 110c which extends like a straight line upward from the top of this arc spring part 110b and a contact part 110d which is formed at the tip of the linear spring part 110c. A socket terminal pin 110e sticks out vertically downward from the bottom of the base edge 110a.
An upper surface of the base 108 extends out in an upward direction from the center of the base parallel with the linear spring part 110c of the contact 110, thereby constituting the an included wall part 112. Contact part 110d of contact 110 is directly adjacent a flat surface at the top of this wall part 112. On the inner side of the wall part 112, there is provided a partition wall 114 for the purpose of preventing any contact between the neighboring contacts 110. Guides 120 are erected at the four corners of the upper surface of the base 108 for the purpose of guiding the carrier 104 on insertion and removal from the socket.
At the time when an IC package 100 is to be mounted on the socket 106, the carrier 104 is inserted to contact the upper surface of the base 108 being positioned by guides 120. The IC package 100 and the carrier 104 are compressed from above with reference to the base 108 by using a tool (which is not shown in the drawings) as diagrammatically shown by an arrow F in FIG. 17.
With such a design with the use of the carrier member, there has been bent leads and alignment problems. When the IC package 100 is mounted on the upper surface of the base 108, the lead 102 is elastically estopped by the contact 110 only on one side of the IC package 100 as is shown in FIG. 17, with a consequence that the IC package 100 is typically slanted at an angle. In such a slanted state, the lead 102 receives a large stress between the contact 110 and the protuberant part 104c which can result in the lead being bent or the IC package 100 escaping from the claw part 104b thereby not being fixed in carrier 104.